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Wildlife
AustralianWildlife
Possums in the Roof
Introduced Species
Wildlife Case Studies
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Introduced species
It is estimated that since European settlement, over 50 mammals and birds, 21 fish and several thousand plants and invertebrates have established viable uncontrolled populations in Australia . These feral species adapt to our conditions very quickly and have very influential effects on Australia 's native wildlife.
WHY ARE INTRODUCED SPECIES SO EFFECTIVE?
A stable environment is seemingly unchanging. Many stable species exist in harmony, negligibly affecting other species and the environment. As a result change is slow. Species become long lived, since genetic change is not important, and as a result put more energy into living than reproduction. When a new species arrives, this stability is upset.
Introduced animals compete with natives for food and habitat. The competition can be direct - i.e. two species that eat the same food, or live in the same nest area. Indirect competition also exists - where one species for example eats the food that another species uses for shelter. Successful introduced species are generally opportunistic, they have short life spans and high population size so they can genetically change quickly with changing environmental parameters. This allows a quick adaptation to a new environment, particularly in relation to exploiting human related habitats.
Introduced species often prey on, or spread foreign disease to our native animals since these species have no defense against the previously unknown. The introduced species often, as a result, have superior reproductive and defensive skills. These skills are an advantage to a stable environment as they are new, therefore can create dramatic changes before the other species have time to adapt to them. Additionally, being new to an environment means that they have no natural predators to keep the population size under control.
Being opportunistic, successful introduced species generally have higher reproduction rates; they mature earlier and have more fertile seasons throughout their life span than the average comparable native species. Opportunistic species deliver more smaller well developed babies that need little parental care, leaving more time for the parent to reproduce again.
All of these options enable an introduced species to enter a relatively stable environment and create havoc among the native counterparts and the stable environment as a whole. Eradication of these species is only possible at an early stage, and once a population has become established there is little prospect of acceptable control methods becoming available.
PROBLEM SPECIES IN AUSTRALIA
According to the Natural Resources and Environment guidelines none of these species should be maintained and released to the wild:
- Feral Dog Common Starling
- Feral Cat Spotted turtle dove
- Rabbit or hare Feral pigeon
- Fox House and Tree Sparrow
- Cane toad European Gold Finch and Green Finch
- Feral goat Common Blackbird
- House and field mouse Common (Indian) Myna
- Feral pig
PIGEONS AND DOVES
Pigeons and doves are seen all over the world, particularly in urban environments where they are known for the damage they cause to city buildings and park benches! In addition, they compete with other birds for nest sites and food, often forcing native birds to leave. Originally beginning along the South Eastern coastline of Australia , the spotted turtle dove for example, is responsible for competition and subsequent relocation of native birds as far inland as Alice Springs .
Furthermore, the feral pigeon is known to spread potentially fatal avian diseases to our native wildlife. Approximately 72% of Adelaide 's feral pigeons are infected with Psittacosis (Pigeon Fanciers Disease) which is easily transferred to native birds and humans.
EUROPEAN RABBIT
Rabbits have on average 30 kittens a year. Their gestation period is only 30 days, and a new litter can be conceived the same day that the female gives birth.
Rabbits were brought into Australia from England for sport. In 1863 a captive colony was released into the Australian bush by a fire. The population spread quickly, reaching Western Australia by 1894, despite efforts to reduce the spread by erecting thousands of kilometres of rabbit proof fences. The rabbit's main form of damage is to agricultural crops, generally due to grazing however they are also responsible for localised soil erosion and salt encroachment. In some areas rabbits have adapted so well they have become plagues, destroying vast areas of farmland, leaving many animals without food or shelter.
EUROPEAN FOX
The red fox is native to the Northern Hemisphere. They colonised Western Australia in the early 1930's, living in a wide variety of habitats from major cities to sand dunes to scrubland. Foxes breed annually, usually having a litter of 4 after 52 days of pregnancy.
Foxes are a typical example of a superior hunter. They have no natural predators in Australia to regulate their population. Furthermore they have overcome our natural carnivores with their superior hunting skills and diet modifications. Foxes are opportunistic feeders - where many predators, such as cats or dingoes starve due to food shortages, the fox regularly scavenges for rubbish, insects or fruit as an alternative resource.
Foxes do not directly alter the environment like rabbits do but are well known for their predation on livestock, particularly fowl and lamb. What is not as commonly known is their effect on our native species. The fox is believed to have contributed to the decline of Australia 's natural predators, such as the quoll, as well as posing a threat to the long-term survival of a range of smaller mammals that they prey upon.
FERAL DOG AND CAT
Like foxes, feral/stray dogs and cats are also predators on our native wildlife. It is important for the human population to control these species as effectively as other introduced pests. Domestic dogs and cats should be confined to their residences both during the day and at night. Dogs should be walked on a leash and all feral cats should be trapped. It is imperative that desexing of pets should be foremost in attaining complete biological control of these potential-pests.
As you can see, most of the animals listed above fall into the opportunistic, quick reproduction species that create such a problem to our unique ecosystems. Our slow growing, slow reproducing native animals are at a distinct disadvantage in competition. To do our part in eradicating these pests, all the species listed above are euthanased on arrival at Lort Smith animal hospital.
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